poj 2513Colored Sticks

http://poj.org/problem?id=2513

 1 #include<cstdio>

 2 #include<cstdlib>

 3 #include<cstring>

 4 using namespace std;

 5 

 6 const int sign_node=26;

 7 const int max_node=550000;

 8 int f[max_node];

 9 int du[max_node];

10 int num=0;

11 int ch[max_node][sign_node];

12 int val[max_node];

13 

14 struct Trie

15 {

16     int sz;

17     void clear(){sz=1; memset(ch[0],0,sizeof(ch[0]));}

18     int idx(char c) {return c-'a';}

19 

20     int insert(char *s)

21     {

22         int u=0,n=strlen(s);

23         for(int i=0; i<n; i++){

24             int c=idx(s[i]);

25             if(!ch[u][c]){

26                memset(ch[sz],0,sizeof(ch[sz]));

27                val[sz]=0;

28                ch[u][c]=sz++;

29             }

30             u=ch[u][c];

31         }

32         if(!val[u]) val[u]=++num;

33         return val[u];

34     }

35 };

36 

37 int find(int x)

38 {

39     if(x!=f[x])

40     f[x]=find(f[x]);

41     return f[x];

42 }

43 

44 void merge(int x,int y)

45 {

46     int fx=find(x);

47     int fy=find(y);

48     if(fx!=fy){

49         f[fx]=fy;

50     }

51 }

52 

53 void inti()

54 {

55     memset(du,0,sizeof(du));

56     for(int i=0; i<=max_node; i++)

57       f[i]=i;

58 }

59 

60 int main()

61 {

62     Trie trie;

63     char a[100],b[100];

64     inti();

65     trie.clear();

66     while(scanf("%s%s",a,b)!=EOF)

67     {

68         int id1=trie.insert(a);

69         int id2=trie.insert(b);

70         du[id1]++;

71         du[id2]++;

72         merge(id1,id2);

73     }

74     int ans=0,ans1=0;

75     for(int i=1; i<=num; i++)

76     {

77         if(du[i]&1)

78         ans++;

79         if(ans>2||find(1)!=find(i))

80         {

81             printf("Impossible\n");

82             return 0;

83         }

84     }

85     if(ans==1)

86     printf("Impossible\n");

87     else

88     printf("Possible\n");

89     return 0;

90 }

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